Diagnosis: tendon rupture. To prevent this, a regular health check is recommended. With the thick rubber joint commonly referred to as the "power joint" - originally produced by the Boge company as a bearing element in engine construction - the check is easy: simply bend it back and forth all round - if there is cracked elephant skin anywhere, the end is imminent. The "tendon", the thinner urethane tendon, on the other hand, tends to fail - if at all - in the dark, namely where the bolts pierce the tendon.
Surf tester Manuel Vogel, an extreme surfer even in winter, does the check every year before the cold season. There's no arthroscopy, only unscrewing helps. "But that only takes ten minutes, including any replacement". With a power joint, on the other hand, the pins at the top of the thread are glued very tightly, so the only way to replace them is often "boiling" and brute force. However, "power joints" usually last longer than tendons, which can compensate for the disadvantage when replacing them. "For normal surfers who don't land high backloops every minute all year round, both the power joint and the string usually last for many years without visible wear," says Frank Lewisch, another surf tester and shop salesman, who knows from experience. However, the "Tendon" is still superior when it comes to ease of servicing.
On the water, the more direct power transmission speaks in favour of this stiffer version - racers don't use anything else - the softer, thicker power joint dampens more comfortably and thus protects the board and surfer in rough conditions - even if the differences are not hugely noticeable.